清除浮动的三种方式

.clearfix:before, .clearfix:after {
content:"";
display:table;
}
.clearfix:after{
clear:both;
overflow:hidden;
}
.clearfix{
    zoom:1;
}

.clear:after{
    display: block;
    content: "";
    clear: both;
    /*visibility: hidden;*/
    /*height: 0;*/
}